Jockey wheels - Page 3

Ray Heindl wrote:
> "Skitt" wrote:
>> Rick Onanian wrote:
>>> Skitt wrote:

>>>>> I don't know what a linear accelerator is, but it sure sounds cool. What is it?
>>>>
>>>> Type the phrase into the box provided by MWCD10 at www.m-w.com and you'll find out.
>>>
>>> So, it's a particle accelerator that doesn't go in circles? How long does a linear accelerator
>>> have to be in order to be useful?
>>
>> Gosh, I wouldn't know. The one at Stanford is two miles long.
>
> The one in the Netherlands is used for medical purposes, so they probably don't need TeV
> energy levels -- they want to cure people, not annihilate them. I suspect it's a bit less than
> 2 miles long.

The MIT Bates linear accelerator is only 160 meters long.
--
Skitt (in Hayward, California) www.geocities.com/opus731/

Ray Heindl <rheindl@nccwx.net> writes:

> The one in the Netherlands

Which one is that? NIKHEF talks about running experiments at CERN, SLAC, FermiLab, and CERN, but
doesn't mention using one in their own back yard.

> is used for medical purposes, so they probably don't need TeV energy levels -- they want to cure
> people, not annihilate them. I suspect it's a bit less than 2 miles long.

Well, sure. They'd do it in kilometers.

--
Evan Kirshenbaum +------------------------------------ HP Laboratories |It is a popular delusion
that the 1501 Page Mill Road, 1U, MS 1141 |government wastes vast amounts of Palo Alto, CA 94304
|money through inefficiency and sloth. |Enormous effort and elaborate kirshenbaum@hpl.hp.com
|planning are required to waste this
(650)857-7572 |much money
| P.J. O'Rourke
http://www.kirshenbaum.net/

On Wed, 17 Sep 2003 17:18:09 GMT, jobst.brandt@stanfordalumni.org wrote:

>Dan Daniel writes:
>
>>> Below are crude illustrations of the upper halves of each pulley with a tooth on top. Only the
>>> tooth is worn, not the other parts.
>
>>> | _|_
>>> / \ | |
>>> / \ | |
>>> / \ / \
>>> | | | |
>>> ------------ -----------
>
>>> narrow g-pulley
>
>>> Obviously, Shimano thought that there was some functional difference. The only thing that I can
>>> think of is that the lower pulley where the chain arrives from the front gears might be blockier
>>> and thicker without causing any trouble, but the pulley where the chain exits to the rear cogs
>>> might somehow profit from being narrower to allow the chain to flex sideways without wearing the
>>> pulley?
>
>>> Regrettably, I paid no attention when removing the pulleys on three different LeTours, so I
>>> don't know which pulley was upper or lower.
>
>> The 'G-Pulley' is for the upper/jockey and the other is for the lower/tension. That is Shimano's
>> system and designation.
>
>These designations don't come out of Shimano engineering but rather from their USA contacts who are
>no more savant than the average wreck.bike contributor, many of whom prefer bicycle jargon to plain
>English. The more bicycle jargon the more exclusive the club.
>

So all the exploded views of derailleurs put out by Shimano that use these terms are pure marketing
and have no basis in any engineering? That's a strange company, that goes to all the trouble to
make such diagrams, lets the US marketing people design and install two different pulley designs,
and lets the same people do all the labeling in order to make themselves part of some exclusive
jargon club.

So tell me, what *is* the source for the designations in the Shimano diagrams, and on what do you
base this assertion of yours?

Carl Fogel wrote:

I wrote:

>>>I've always understood the term "jockey pulley" to refer to the upper pulley.
>>
>>>The lower is called the "tension pulley."

Andy Muzi wrote:
>
> Hmmm. I find "upper" and "lower" pulley sufficient.
>
> Do you really say "jockey pulley" when writing service with a non-afficionado?

Certainly not, but the O.P. asked what the term meant.

Jobst Brandt wrote:

>>I don't use the term for either wheel because it is undefined. I find it used to refer to either
>>of the two idler wheels. Idler is in contrast to drive sprockets, since some early derailleurs
>>used sprockets for these wheels. In many derailleurs they are identical parts as they were in all
>>the early ones by Campagnolo, Huret, Simplex and others.

Carl Fogel wrote:

> Is there any mechanical difference between the two pulleys? That is, might one be expected to
> handle a different load?
>
> I'm curious because I recently replaced a badly worn pair on a Schwinn LeTour by robbing parts
> from spare LeTours that I bought for that purpose and for visiting friends to ride.
>
> To my surprise, the upper and lower 10-tooth plastic pulleys are different parts. One is stamped
> on both sides "SHIMANO NARROW" and has a noticeably narrower profile. The other is stamped
> "SHIMANO CENTERON G-PULLEY NARROW" and has a thicker shoulder extending to the base of the worn
> plastic teeth.
>
> Below are crude illustrations of the upper halves of each pulley with a tooth on top. Only the
> tooth is worn, not the other parts.
>
> | _|_
> / \ | |
> / \ | |
> / \ / \
> | | | |
> ------------ -----------
>
> narrow g-pulley
>
> Obviously, Shimano thought that there was some functional difference. The only thing that I can
> think of is that the lower pulley where the chain arrives from the front gears might be
> blockier and thicker without causing any trouble, but the pulley where the chain exits to the
> rear cogs might somehow profit from being narrower to allow the chain to flex sideways without
> wearing the pulley?
>
> Regrettably, I paid no attention when removing the pulleys on three different LeTours, so I don't
> know which pulley was upper or lower.

Nice ASCII art! The blockier pulley is the upper (jockey) pulley. The fatter "teeth" control the
chain better because they're a snugger fit into the chain, so the chain doesn't slop back and
forth on them.

The pointy pulley is the lower (tension) pulley. The teeth are narrow and pointed so that they'll
engage the chain smoothly even when the chain is approaching the derailer at an angle due to
different gear positions.

I believe SunTour was the first to use this profile difference.

The old Benelux derailers used a more sprocket-like upper pulley, and a round, toothless bottom
pulley, presumably for the same reason. I've actually used old Benelux pulleys on modern Shimano
derailers with good results...they have adjustable ball bearings, and I've never found Shimano's
"Centeron" slop in the upper pulley to be of any great utility in a properly adjusted system.

Jobst:

> I'm sure you have gotten instruction manuals for foreign made goods that were difficult to
> decipher. The proper way to write them is to get a well versed native to translate it. In that
> regard, finding technically versed people in the bicycle business is difficult, although many are
> willing to offer their services.

As to the origin of the usage "jockey" and "tension" pulleys, you can't hang that on Shimano. I
don't recall exactly where I first encountered these terms, but I belive it would have been with the
instructions for the first derailer I ever bought, a British Benelux Mark VIII, circa 1959.

I've heard that the translation problem with Japanese companies is complicated by a concern lest
their in-house translators lose "face". This results in such solecisms as calling brake calipers
"arches" as well as clumsy locutions like "crank arm."

Sheldon "Pulleys" Brown +---------------------------------------------------+
| Even if you do learn to speak correct English, | whom are you going to speak it to? | --Clarence
| Darrow |
+---------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

On Thu, 18 Sep 2003 01:24:12 GMT, Dave Lehnen <dclehnen@worldnet.att.net> wrote:

>> It depends on the included angle between entry and exit of the chain, and its tension. Since
>> tension is the same, only the angle between the two chain lines has a differentiating effect.
>> That would be T * sin A = idler load.
>>
><snip>
>
>2T * cos (A/2) = idler load, if A is the included angle between chains, and (180 deg. - A) is the
>chain wrap angle. Load is zero for the case of 0 deg. chain wrap and 2T for 180 deg. of wrap.
>
>Dave Le

Pardon my inability to fully understand. I have a cassette with a 19t cog. It is actually the 19,21
together on a Record Ti. cassette. The 19t cog only skips on occasion with the 39t ring and never
with the 53. If the chainring were 42 or 34 might the cog not slip?

> >Dan Daniel writes:
> >
> >>> Below are crude illustrations of the upper halves of each pulley with a tooth on top. Only the
> >>> tooth is worn, not the other parts.
> >
> >>> | _|_
> >>> / \ | |
> >>> / \ | |
> >>> / \ / \
> >>> | | | |
> >>> ------------ -----------
> >
> >>> narrow g-pulley
> >
> >>> Obviously, Shimano thought that there was some functional difference. The only thing that I
> >>> can think of is that the lower pulley where the chain arrives from the front gears might be
> >>> blockier and thicker without causing any trouble, but the pulley where the chain exits to the
> >>> rear cogs might somehow profit from being narrower to allow the chain to flex sideways without
> >>> wearing the pulley?
> >
> >>> Regrettably, I paid no attention when removing the pulleys on three different LeTours, so I
> >>> don't know which pulley was upper or lower.
> >
> >> The 'G-Pulley' is for the upper/jockey and the other is for the lower/tension. That is
> >> Shimano's system and designation.

> On Wed, 17 Sep 2003 17:18:09 GMT, jobst.brandt@stanfordalumni.org
> >These designations don't come out of Shimano engineering but rather from their USA contacts who
> >are no more savant than the average wreck.bike contributor, many of whom prefer bicycle jargon to
> >plain English. The more bicycle jargon the more exclusive the club.

"Dan Daniel" <ddandan@pacbell.net> wrote in message
news:h29imvsi85ah3hrbmf0dsp1c5fl4rsmh9b@4ax.com...
> So all the exploded views of derailleurs put out by Shimano that use these terms are pure
> marketing and have no basis in any engineering? That's a strange company, that goes to all the
> trouble to make such diagrams, lets the US marketing people design and install two different
> pulley designs, and lets the same people do all the labeling in order to make themselves part of
> some exclusive jargon club.
>
> So tell me, what *is* the source for the designations in the Shimano diagrams, and on what do you
> base this assertion of yours?

I'm sorry to report that Jobst is mistaken. Those are two different features, introduced at about
the same time. He mixed them in his post.

Shimano at one time included a stiff spring in the anchor assembly of the rear derailleur such that
one might preselect a gear at the shifter. The derailleur would complete that shift once the pedals
moved again. That was on the "L" series in the early eighties.

The "Centeron" idler and the similar design found on almost all modern changers automatically
centers the chain under a cog within a millimeter or so and makes shifting smoother than it would
otherwisw be. Helps friction shifting too!

So, back to your question-- Put the one with sideplay in top. Campagnolo handily labels theirs
"upper" and "lower" in plain English.
--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Dan Daniel writes:

>>>> Regrettably, I paid no attention when removing the pulleys on three different LeTours, so I
>>>> don't know which pulley was upper or lower.

>>> The 'G-Pulley' is for the upper/jockey and the other is for the lower/tension. That is Shimano's
>>> system and designation.

>> These designations don't come out of Shimano engineering but rather from their USA contacts who
>> are no more savant than the average wreck.bike contributor, many of whom prefer bicycle jargon to
>> plain English. The more bicycle jargon the more exclusive the club.

> So all the exploded views of derailleurs put out by Shimano that use these terms are pure
> marketing and have no basis in any engineering? That's a strange company, that goes to all the
> trouble to make such diagrams, lets the US marketing people design and install two different
> pulley designs, and lets the same people do all the labeling in order to make themselves part of
> some exclusive jargon club.

There is nothing strange about that. They have the option to do their own translation that
usually sounds like a foreign type of English or they can rely on the bicycle "experts" in the
USA, or worse, from the land of bicycle jargon, England. As an example, my first job at Porsche
KG was to translate their 356 Shop manual into technically correct English after it had
previously been translated in Germany. They were aware of the problem because they often got
comments from the US dealers.

I'm sure you have gotten instruction manuals for foreign made goods that were difficult to decipher.
The proper way to write them is to get a well versed native to translate it. In that regard, finding
technically versed people in the bicycle business is difficult, although many are willing to offer
their services.

> So tell me, what *is* the source for the designations in the Shimano diagrams, and on what do you
> base this assertion of yours?

I base that on Campagnolo and Japanese camera manuals that I have read. When I see Shimano
literature with colloquialisms I detect an American bicyclist's translations.

Jobst Brandt jobst.brandt@stanfordalumni.org

Quoth Paul Kopit:

> ...I have a cassette with a 19t cog. It is actually the 19,21 together on a Record Ti. cassette.
> The 19t cog only skips on occasion with the 39t ring and never with the 53. If the chainring were
> 42 or 34 might the cog not slip?

Your 19 sprocket is probably worn out. Worn-out sprockets tend to skip, but only when the chain
tension reaches a certain level. The more worn out the sprocket, the lower the tension level
required to cause skipping.

Chain tension is inversely proportional to the chainring size, so for the same amount of foot force,
the chain tension is 36% higher when you're on your 39.

Given common realities of gear usage, you also probably pedal harder when you're in the 39/19 than
in the 53/19, so it's not surprising that you only notice the skipping in the former combination. If
you continue riding without replacing the worn parts, the problem will gradually get worse.

Sheldon "Time For A New Cassette And Chain" Brown
+---------------------------------------------------------+
| I don't like spinach, and I'm glad I don't, because | if I liked it I'd eat it, and I just hate
| it. | --Clarence Darrow |
+---------------------------------------------------------+ Harris Cyclery, West Newton,
Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts
shipped Worldwide http://captainbike.com http://sheldonbrown.com

Paul Kopit <p.kopit@verizon.net> writes:

>> It depends on the included angle between entry and exit of the chain, and its tension. Since
>> tension is the same, only the angle between the two chain lines has a differentiating effect.
>> That would be: 2T * cos (A/2) = idler load, if A is the included angle between chains, and (180
>> deg. - A) is the chain wrap angle. Load is zero for the case of 0 deg. chain wrap and 2T for 180
>> deg. of wrap.

> Pardon my inability to fully understand. I have a cassette with a 19t cog. It is actually the
> 19,21 together on a Record Ti. cassette. The 19t cog only skips on occasion with the 39t ring and
> never with the 53. If the chainring were 42 or 34 might the cog not slip?

This has nothing to do with sprockets, only the with the load on the idler wheels of a derailleur.

Chains do not "slip" they being digital devices, they skip a whole tooth or more. Slip is a
frictional analog process. Chain skip is caused by sprocket wear from an elongated (worn) chain that
rides higher on the tooth than a chain in correct pitch will. When a new chain is subsequently used,
it rides in the wear marks made by the longer pitch chain making the sprocket, in effect, have too
large a pitch, one that the new chain will not engage under load. It is on the engagement (incoming)
end that the chain fails to engage the sprocket and subsequently skips over to drop into the next
engagement.

Jobst Brandt jobst.brandt@stanfordalumni.org

Excellent description. Was this something that was patented, and owned by some company (maybe
shimano or suntour?) Or was it just a design feature that was quickly copied once competitors
figured out its purpose ??

- Don

"A Muzi" <am@yellowjersey.org> writes:

>> >Dan Daniel writes:

>> >>> Below are crude illustrations of the upper halves of each pulley with a tooth on top. Only
>> >>> the tooth is worn, not the other parts.
>> >
>> >>> | _|_
>> >>> / \ | |
>> >>> / \ | |
>> >>> / \ / \
>> >>> | | | |
>> >>> ------------ -----------
>> >
>> >>> narrow g-pulley

>I'm sorry to report that Jobst is mistaken. Those are two different features, introduced at about
>the same time. He mixed them in his post.

>Shimano at one time included a stiff spring in the anchor assembly of the rear derailleur such that
>one might preselect a gear at the shifter. The derailleur would complete that shift once the pedals
>moved again. That was on the "L" series in the early eighties.

>The "Centeron" idler and the similar design found on almost all modern changers automatically
>centers the chain under a cog within a millimeter or so and makes shifting smoother than it would
>otherwisw be. Helps friction shifting too!

>So, back to your question-- Put the one with sideplay in top. Campagnolo handily labels theirs
>"upper" and "lower" in plain English.
>--
>Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Sheldon Brown writes:

>> ...I have a cassette with a 19t cog. It is actually the 19,21 together on a Record Ti. cassette.
>> The 19t cog only skips on occasion with the 39t ring and never with the 53. If the chainring were
>> 42 or 34 might the cog not slip?

Don't use Titanium sprockets.

> Your 19 sprocket is probably worn out. Worn-out sprockets tend to skip, but only when the chain
> tension reaches a certain level. The more worn out the sprocket, the lower the tension level
> required to cause skipping.

> Chain tension is inversely proportional to the chainring size, so for the same amount of foot
> force, the chain tension is 36% higher when you're on your 39.

> Given common realities of gear usage, you also probably pedal harder when you're in the 39/19 than
> in the 53/19, so it's not surprising that you only notice the skipping in the former combination.
> If you continue riding without replacing the worn parts, the problem will gradually get worse.

But no. The chain will wear, it's pitch getting longer, and it will begin to fit the larger pitch
diameter of the worn sprocket. However, I wouldn't put up with the skipping in the meanwhile.

Jobst Brandt jobst.brandt@stanfordalumni.org

Andrew Muzi writes:

> I'm sorry to report that Jobst is mistaken. Those are two different features, introduced at about
> the same time. He mixed them in his post.

> Shimano at one time included a stiff spring in the anchor assembly of the rear derailleur such
> that one might preselect a gear at the shifter. The derailleur would complete that shift once the
> pedals moved again. That was on the "L" series in the early eighties.

I disagree. The wobbly wheel allows the derailleur to move to the next gear position before the
chain makes the move. This allows not only the original concept of pre-shifting for non pedalers,
but it allows quicker shifts in which the indexed lever is moved quickly to the desired gear
position, regardless of chain speed. It's origins came from the desire to shift while not pedaling
but benefits remain for shifting in general.

> The "Centeron" idler and the similar design found on almost all modern changers automatically
> centers the chain under a cog within a millimeter or so and makes shifting smoother than it would
> otherwise be. Helps friction shifting too!

Wait a minute. Does it benefit shifting or silent running once in gear? These refinements miss my
enthusiasm. Unless stalled on a steep bump, my chain speed is enough to make shifting go as fast
as I can move the lever. The wobbly wheel cannot make up for derailleur misalignment because if it
were out of correct position, shifting in one or the other direction would be unreliable... for
all gears.

> So, back to your question-- Put the one with side play in top. Campagnolo handily labels theirs
> "upper" and "lower" in plain English.

Yes, just like 'left' and 'right' sides of the wheel or bicycle rather than 'drive-side' and
'non-drive-side'.

Jobst Brandt jobst.brandt@stanfordalumni.org

Quoth Andy Muzi:

> Shimano at one time included a stiff spring in the anchor assembly of the rear derailleur such
> that one might preselect a gear at the shifter. The derailleur would complete that shift once the
> pedals moved again. That was on the "L" series in the early eighties.

This was a great feature, which Shimano has unfortunately abandoned, but it considerably predates
the "L" series.

The overload spring was featured on the Lark and Eagle derailers of the 1970s (These inexpensive
units were heavy, but nearly indestructible, and shifted notably better than anything else available
in the '70s.)

This feature was actually introduced, I believe, for the benefit of children's wheelie bikes with
"stick shift" shifters. The main purpose was to prevent cable breakage when a clueless adolescent
yanked on the shift lever while stopped.

The really clever thing about this was how Shimano was able to implement it without actually adding
an additional spring...it used the "dead" end of the spring that moved the derailer parallelogram.

Sheldon "Can't Figure Why They Discontinued This Feature" Brown
+---------------------------------------------------------------------+
| A man of character finds a special attractiveness in difficulty, | since it is only by coming to
| grips with difficulty | that he can realize his potentialities. -- Charles DeGaulle |
+---------------------------------------------------------------------+ Harris Cyclery, West Newton,
Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts
shipped Worldwide http://captainbike.com http://sheldonbrown.com

jobst.brandt@stanfordalumni.org wrote:

> Rear wheels don't have a left and right side, but rather "drive-side" and "non-drive-side".

That usage is hard to fault, since whether the drive is on the right or on the left depends on the
viewer's vantage point. You can arbitrarily designate one "correct" frame of reference, but others
may not, and that can lead to confusion.

Consider that these so-called "jargon" terms arise for a reason, to dispel misunderstanding. I
have a left arm and my bike has a crank, but when I say "left crank arm" I am understood, object
though you may.

Chalo Colina

Chalo Colina writes:

>> Rear wheels don't have a left and right side, but rather "drive-side" and "non-drive-side".

> That usage is hard to fault, since whether the drive is on the right or on the left depends on the
> viewer's vantage point. You can arbitrarily designate one "correct" frame of reference, but others
> may not, and that can lead to confusion.

I had no idea you could not tell left from right depending on which way you face. That's
extraordinary. I suppose when you face someone his left and right change to right and left in
contrast to when standing behind him.

> Consider that these so-called "jargon" terms arise for a reason, to dispel misunderstanding. I
> have a left arm and my bike has a crank, but when I say "left crank arm" I am understood, object
> though you may.

Not at all. Jargon is like the secret handshake of the initiated. The less others understand the
more important the discourse. What ever you do, don't ask what is meant by such talk or you'll fall
into the trap of ridicule. How could you!

Jobst Brandt jobst.brandt@stanfordalumni.org